I have a bluish-gray "ring" that develops in my toilet bowls, more evident towards the upper area of the water level.

It really doesn't come off. It feels like a stain within the porcelain, as there is no crust, etc. Vinegar or bleach have no effect. I tried scrubbing the ring with Fast Orange with pumice, and it did notably remove some of bluing, but not all.

There is no blue coloring used in the water, which comes from a well, through a softener I got from Speedbump (Fleck and Clack, Resintech beads, rock salt), but I think this was starting before I added the softener.

Photo shows it with the water level down before I started cleaning it.

Actually, there wasn't much scrubbing involved. I used a small paintbrush, going back and forth. I am a lazy guy, and wanted to see if they worked chemically, since the stain seemed to be in the porcelain, not to be felt by scraping with a fingernail.

I've been using bleach to whiten the porcelain sink bowls in my kitchen after scrubbing them well with a brush and dish soap. The bleach does help whiten the porcelain and doesn't seem to leave any damage.

So....I was curious if it would have any effect on the blue-grey rings that appeared in the toilet bowls after I replaced some old iron piping with new copper. I scrubbed the toilet as usual and flushed it. Once the bowl was filled with fresh clean water, I added about a quart of bleach, trying to avoid adding too much and flushing it. Then I let it sit overnight, about 8 hours.

Came back, and viola, the ring was gone! For what it's worth, I used Concentrated White Cloud brand, which was the cheapest I saw on sale at Wal-Mart.

I have had the blue stain problem personally. The problem was my 176' 4" well which was in place before I bought the home; took a dump. It was drilled with black iron casing which had a broken coupling at about 40'. I knew this because when the pump died, we pulled it and then we could hear surface water pouring into the casing through the broken coupling. It must have taken 20 years for the surface water to find it's way down to that coupling, but when it did it got to running in pretty fast. A few months before the pump died, my Wife complained about the water tasting bad, then the blue staining appeared. Surface water in my area has a PH of 5.5. It's very acidic, it eats the copper slowly and that is what leaves the blue stain. You should have your PH checked. If it's not above 6.8 or so, it would be a good idea to put in an acid neutralizer. It will raise the PH up to acceptable levels and stop the staining.